1. Field of the Invention.
The present invention relates to heat exchangers having low pressure drop and high efficiency and primarily used for air to air heat exchange.
2. Description of the Prior Art.
In the prior art various types of heat exchangers have been advanced. Examples of patents showing exchangers include U.S. Pat. No. 3,705,621, which has two passes of each of the cooling tubes across the heat exchanger between an inlet and outlet header. U.S. Pat. No. 3,428,117 shows a heat exchanger that has pipes which are curved back and forth from the input manifold or header so that they have five lengths of pipe extending across the exchanger. This is designed specifically for nuclear power plants, and involves quite expensive construction.
U.S. Pat. No. 3,063,682 shows a heat exchanger that has tubes that are curved back and forth across the heat exchange area so that the supply and return headers or pipes are on the same side of the exchanger. However, the tubes have axes which lie in a single laterally extending plane.
U.S. Pat. No. 3,020,024 shows a plurality of tubes on the inlet and outlet sides of an exchanger that merely go out and double back from the inlet to the outlet. At the inlet chamber there are four stacked tubes that extend out at the end of the heat exchanger and then back.
The use of a cross flow of cooling air that goes generally transverse to the longitudinal axes of tubes carrying the fluid to be cooled is also known. Problems exist because of high pressure drops in the exchanger where low pressure air needs to be cooled while using a minimum of space for the heat exchanger.